Clarify SW103 migration with concrete examples and keyed-only registration guidance

[Copilot]

This updates SW103 documentation to directly address migration ambiguity called out in review feedback. The rule guidance now shows exactly how to move from Microsoft.Extensions.Azure patterns to keyed DI and explicitly discourages fallback unkeyed registrations.

• Migration examples added

  • Added concrete before/after registration examples:
    • AddAzureClients(...).WithName(...) usage
    • equivalent keyed DI registrations for Azure SDK clients
  • Added concrete before/after DI callsite examples:
    • IAzureClientFactory<T>.CreateClient("key")
    • [FromKeyedServices("key")] constructor injection

• Keyed-only preference made explicit

  • Added a review-point note to prefer keyed singleton registrations for Azure SDK clients.
  • Explicitly calls out to avoid default unkeyed registration for the same client type.

// Preferred direction
builder.Services.AddKeyedSingleton<BlobServiceClient>("blob-storage", (sp, _) =>
    new BlobServiceClient(builder.Configuration.GetConnectionString("BlobStorage")));

public class BlobUploadService(
    [FromKeyedServices("blob-storage")] BlobServiceClient blobClient)
{
    private readonly BlobServiceClient _blobClient = blobClient;
}

[cliedeman]

add some migration samples to the repo.

DI callsites and AddAzureClients config

[Copilot]

Done — added four concrete code samples to the Migration Notes section:

1. Registration before — full AddAzureClients block with two named clients (blob-storage, order-queue) and configuration sections.
2. Registration after — equivalent AddKeyedSingleton registrations using connection strings, no Microsoft.Extensions.Azure import.
3. DI callsite before — constructor injection via IAzureClientFactory<BlobServiceClient> + CreateClient("blob-storage").
4. DI callsite after — constructor injection using [FromKeyedServices("blob-storage")] attribute.